The present invention relates to a charge or charging device for charging a storage cell.
A conventional charge device has a storage cell terminal to be connected to the storage cell, a trickle charge terminal for receiving a trickle charge voltage of a power supply, a boost charge terminal connected to the storage cell terminal for receiving a boost charge voltage of a boost charge circuit, and a constant current circuit connected between the storage cell terminal and the trickle charge terminal for causing a constant current to flow from the trickle charge terminal to the storage cell terminal.
In the conventional charge device, the boost charge circuit includes a charge completion detector for detecting a change in a terminal voltage of the storage cell to produce a charge completion signal when the change becomes larger than a reference level. In the conventional charge device, both the boost charge voltage and the trickle charge voltage are supplied to the storage cell. Inasmuch as the boost charge circuit charges the storage cell while the storage cell is supplied with the trickle charge voltage, the rate of the change of the terminal voltage becomes slower. A the charge completion detector detects the slow rate of the change. As a result, the storage cell is charged too much and the lifetime of the storage cell is decreased.